Page:Popular Science Monthly Volume 91.djvu/458

 442

��Popular Science Monthly

��alternating current, an aluminum plate rectifier' must be used in series with the battery, together with a small lamp or other suitable resistance. The aluminum plate of the rectifier may consist of a small alumi-

���A type of rectifier used with the battery for charging it from an alternating current

num wire with its point just dipping into the rectifier electrolyte. As the battery is small, the charging current must also be small. A gentle bubbling at the plates is sufficient. This battery does not hold its charge very long but it is a simple matter to charge it each time before use, as a double throw switch will change the current to the charging circuit or to the apparatus quickly. — R. V. Wilson.

��Wireless Signals Transmitted by Telephone

THE diagram shows how I enabled my friend who had no wireless outfit to listen in on my set. I installed a one-wire telephone line between our homes,

V which are about 400 ft. apart. Much to my surprise this in- creased the strength of the signals. , mtmoNE \m

���Wiring diagram of the telephone line show- ing its connection with the wireless set

As an additional pleasure we were able to talk over the telephone while wireless mes- sages were coming in. — C. Wiltsee Tufts.

��An Effective Method for Recharging Dry Cells

WHAT I have found to be the most effective method for recharging dry cells consists in making over the construc- tion^ the cell and placing it into some container. Such a container may easily be made from a hollow tile such as is used in building construction. These tiles are cut to the height of a dry cell by a hammer and chisel. The tile is m „ tl _ „*,,»„.

then stood upright on"a flat board and enough concrete is poured in to fill the bottom of the tile an inch deep. After the concrete has set, it is coated with a thin layer of melted paraffin which is w then allowed to cool. The bottom of the dry cell is then knocked off and the inside compounds, with the exception of the sealing compound, are then taken out. A number of holes are then punched in the cell, and it with its carbon is then immersed in an "active" solution poured into the tile. This solution is made of sal ammoniac and soft or rain water in the proportion of 4 oz. of sal ammoniac to I qt. of water. — Thomas W. Benson.

���Running Bell-Wires Through Walls with an Umbrella-Rib Bodkin

AN umbrella rib may be made to do . excellent service in running electric bell-wires. Such a rib is not a great deal larger than the diameter of the bell-wire, consequently it can be run through a small hole. The wire is stripped of its covering for a short distance and threaded through the little loop near the end of the rib. The wire is then pressed snugly into the trough of the rib, which can be moved around while searching for the opening without disturb- ing the wire. The ball on the end of the rib facilitates its easy passage through the opening. — James M. Kane.

���Electric bell-wire inserted with umbrella-rib bodkin

�� �